jMonkeyEngine is a game engine made for developers who want to create 3D games following modern technology standards. The framework is programmed entirely in Java, and aimed at wide accessibility and fast deployment to desktop, Web, and mobile platforms. It is not a visual “RPG Maker” or a drag-and-drop “FPS mod”. If you are comfortable writing Java code, you can rely on jMonkeyEngine as your next 3D game’s foundation.
Castle Game Engine is a cross-platform 3D game engine written in Object Pascal. It includes a flexible system of 3D objects, with out-of-the-box levels, items, intelligent creatures, and more. Rendering and processing of 3D models in X3D, VRML, Collada, and other formats is implemented. Many graphic effects are available, including shadows, bump mapping, shaders, mirrors, and screen effects.
RoseThorn is a cross-platform library for 2D and 3D games running on GNU/Linux (and possibly other Unix-like OSes) and Windows. Features include: hardware accelerated 2D and 3D rendering; Ogg and WAV Sound support with OpenAL; Lua scripting; BMP, JPEG, and PNG image loading and saving (from screenshots); easily created and modified user interfaces with XML and CSS, combined with Lua event handling; separate 2D and 3D libraries; support for multiple fonts in both TTF and bitmap formats; support for OBJ, 3DS, MD5, and RTM model formats; skeletal animation (a work in progress); support for UDP and TCP networking; thread and mutex support; a Simple Shader API; 2D animated sprites; and some basic cryptography support. There is simple event management, with key/mouse bindings easily customized from the in-game console, config file, command line, or GUI.
Revised is a visual editor (or wizard/assistant/GUI) for Ren’Py, the visual-novel game editor. Ren'Py has a lot of capabilities, and Revised's purpose is not to allow everything that Ren'Py can do, just some of the basics. You can think of it as a step-by-step wizard to create the skeleton of a Ren'Py game.